A torsional vibration damper, i.e., a dual mass flywheel, is generally used for damping a torsional vibration that is generated from the transmission of power between an output shaft of an engine and an input shaft of a transmission. Typically, torsional vibration dampers include a first mass, a second mass, and a damping unit disposed between the first and second masses. The first mass is connected to the output shaft of the engine, and the second mass is connected to the input shaft of the transmission through a clutch mechanism. The first and second masses are connected to each other through the damping unit such that the first and second masses can rotate relative to each other.
Generally, the engine of a vehicle provides the driving force distributed to the wheels of the vehicle. However, at times the engine may be driven by an inertia force of the vehicle. Therefore, the first and second masses must be designed to rotate in both directions relative to each other.
When engine torque is substantially high and the vehicle is driven with a specific gear ratio, relative rotation between the first and second masses reaches a limit. Furthermore, when the engine torque changes irregularly, the first and second masses may be dashed against a member for limiting the relative rotation of the first and second masses.
To solve such problems, the flywheel is generally designed to have a high level of damping characteristics. In the prior flywheel, when the relative rotation between the first and second masses occurs, the magnitude of torque cannot be regulated. Furthermore, the damping effect of the flywheel is almost constant even when the relative rotation between the first and second masses occurs.
To solve such problems, a flywheel, having a pair of wedge-shaped friction elements that generate a friction force in proportion to the amount of relative rotation between the masses, and a concentrated mass type friction element, which generates a friction force in proportion to the centrifugal force, i.e., rotation speed, has been developed.
However, in a conventional flywheel, the wedge-shaped friction element and the concentrated mass type friction element independently operate, and this makes it difficult to achieve a precise tuning of the damping effect. Additionally, due to friction between the pair of wedge-shaped friction elements, a desired friction cannot be obtained.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.